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Las Oxazaborolidinas Fluoradas Cationicas Quirales. Catalizadores de segunda generación más potentes para reacciones

Karla Mahender Reddy¹, Eswar Bhimireddy¹, Barla Thirupathi¹

¹Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States.

Journal of the American Chemical Society

|January 27, 2016

Resumen

Los investigadores desarrollaron nuevos catalizadores quirales de oxazaborolidinio que mejoran la catálisis enantioselectiva para las reacciones de Diels-Alder. Estos catalizadores mejoran el rendimiento y la enantioselectividad utilizando cargas bajas y son fácilmente recuperables para la síntesis a gran escala.

Área de la Ciencia:

Química orgánica
Catálisis
Síntesis asimétrica

Sus antecedentes:

Los ligandos quirales en la catálisis del ácido de Lewis a menudo reducen la actividad.
La activación de protones o ácido de Lewis puede superar esta desactivación.
Los sustituyentes de fluor ofrecen una estrategia potencial para mejorar el rendimiento del catalizador.

Objetivo del estudio:

Desarrollar una nueva generación de catalizadores quirales con mayor actividad y selectividad.
Investigar el efecto de los sustituyentes de flúor en el rendimiento del ligando quiral en la catálisis.
Para demostrar la utilidad de estos catalizadores en las reacciones de Diels-Alder.

Principales métodos:

Síntesis de nuevas especies catiónicas quirales de oxazaborolidinio que incorporan sustituyentes de flúor.
Coordinación de estos ligandos con los derivados metálicos del ácido de Lewis.
Aplicación de los catalizadores resultantes en varias reacciones de Diels-Alder.
Análisis del rendimiento de la reacción y del exceso enantiomérico (ee).

Principales resultados:

Los nuevos catalizadores alcanzaron altos rendimientos (>95%) y enantioselectividades (>95% ee) en las reacciones de Diels-Alder.
Las cargas del catalizador se redujeron significativamente a 1-2 mol %.
La presencia de sustituyentes de flúor en el ligando quiral aumentó la actividad catalítica.
El ligando quiral demostró una facilidad de recuperación, beneficiosa para aplicaciones industriales.

Conclusiones:

Los catalizadores quirales de oxazaborolidinio sustituidos por flúor representan un avance significativo en la catálisis enantioselectiva.
Estos catalizadores de segunda generación ofrecen un rendimiento y una practicidad superiores para la síntesis a gran escala.
La estrategia de incorporar sustituyentes de flúor proporciona una vía viable para optimizar los catalizadores quirales de ácido de Lewis.

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